Design of Adaptive Threshold Based Fault Detection and Isolation for Attitude Control System of a Three Axis Satellite

This paper presents robust fault detection based on adaptive thresholds for a three axis satellite. For this purpose, first we described the attitude control system (ACS) as a quasi linear parameter model. Next, an interval observer has been designed that based on, effect of the satellite parameter uncertainties has been propagated into the alarm limits and so the adaptive thresholds are generated. In this paper, it is shown that the developed method minimizes the missing alarm rates; also this approach detects small or incipient faults more effectively than the classical fault detection algorithms with constantthresholds. In the next part of paper, we propose an isolation algorithm using the fault tree approach. Also, an accommodation system has been designed based on reconfiguration of available actuators. Accordingly, after isolation of faulty reaction wheels, the accommodation system turns them off and replaces the suitable magnetic tourqers instead of the faulty reaction wheels and so the attitude control error is maintained limited.